Diabetic Retinopathy: A General Survey

Diabetic retinopathy has become one of the major causes of legal blindness and can cause a degree of visual loss that prevents independent ambulation and even total blindness. It-is now the second leading cause of new blindness in the United States and the leading cause in adults under age sixty-five.^1–2 The tragedy of this is even more greatly magnified when one considers that those blinded by diabetes are often quite young, in their twenties or thirties. Fortunately, most patients with diabetic retinopathy do not have visual impairment. The prevalence of diabetic retinopathy is strongly and positively associated with duration of diabetes.^3–5 Retinopathy is seen after a shorter duration of diabetes in older patients than in younger patients, but prevalence figures for all ages seem to merge after ten years duration of diabetes.³ Thus, the overall prevalence of clinically detectable retinopathy in patients under age thirty at diagnosis is less than 10% if the duration of the disease is less than ten years, while the prevalence for patients over age 60 at diagnosis is 35–40% with the same duration.4 After fifteen years duration of diabetes, 60–70% of patients will have retinopathy.^3–5 The true prevalence of diabetic retinopathy remains unknown, however, and statistical data are complicated by a variety of factors. Most studies focus on juvenile-onset diabetes, or of diabetes of long duration, and do not include the large numbers of elderly patients with mild diabetes without retinopathy. Studies have usually been done in referral centers for either diabetes or eye disease. Thus, the prevalence of the disease is probably more common than appreciated by most physicians, but not as common as thought by most ophthalmologists who are biased by the type of diabetic patients referred for ophthalmic care.